It has heretofore been known to the art of water treatment to effect disinfection and reduction in the bacterial content thereof to treat contaminated water, for drinking purposes, for use in swimming pools and for other purposes and in other environments, by passing the same through strong base polyhalide bacteriocidal anion-exchange resins in which the exchange sites of said anion-exchange resins have attached to a predominant number of such sites polyhalide anions, notably triiodide ions, satisfying certain formulae conditions. After suitable preparations of such polyhalide bacteriocidal resins, the contaminated or possibly contaminated water to be treated is passed therethrough to effect decontamination or disinfection thereof.
Among the prior art references which disclose procedures following the approaches which have been referred to above are U.S. Pat. Nos. 3,817,860; 4,187,183; 4,190,529; and published articles appearing in Proceedings Second World Congress, International Water Resources Association, New Delhi, India, December, 1975, Vol. II, pp. 53-59; and Applied Microbiology, Nov. 1970, Vol. 20, No. 5, pp. 720-722.
In U.S. Pat. No. 4,187,183, it has been suggested, generally, that, in the production of the mixed-form polyhalide bacteriocidal resin, there be added to a strong base anion exchange resin a slurry mixture of elemental iodine, interhalogen, or bromine and an appropriate amount of an iodide or bromide salt, and it is pointed out that the preferred amount of iodide or bromide is less than the stoichiometric amount required for complete loading of triiodide or tribromide ions on all available resin sites, and the X.sub.2 :X.sup.- ratio is always greater than one. It points out, further, that iodine or bromine liberated from such bacteriocidal resins during water treatment by the passage of water therethrough may be readily scavenged from said treated water by an unloaded anion-exchange resin, and the hypohalous acid which is formed can be removed by additional treatment with activated charcoal. In the description of the preferred embodiment of the invention of said U.S. Pat. No. 4,187,183, the strong base anion-exchange resin, in chloride or sulfate form, is reacted with a mixture of iodine and a pre-selected amount of iodide salt to form a polyhalide resin product but, while the use of iodine and an iodide salt is thereafter discussed as indicative of the particularly advantageous embodiment of the invention of said patent, bromide or an appropriate interhalogen may be substituted for iodine, and that a bromide salt may be substituted for the iodide salt to produce other resins which are within the scope of the invention of said patent. The particular results obtained and reported are, however, as noted above, directed to the use of iodine and potassium iodide in the production of the polyhalide bacteriocidal resin, and the formulae stated in the claims of said patent are likewise defined in relation to the exchange sites and related facets in terms of the use of iodine and potassium iodide in the production of the polyhalide bacteriocidal resins. Similar disclosures and reports of results appear in U.S. Pat. No. 4,190,529.
The earlier U.S. Pat. No. 3,817,860 also discloses the preparation and utilization of a strongly basic anion-exchange resin containing combined triiodide in insolubilized form in said resin, and the disinfection of contaminated or bacteria-containing water by passage through a bed of a porous granular material or beads comprising said previously prepared triiodide strongly basic anion-exchange resin. The aforesaid U.S. Pat. No. 3,817,860 also refers to an earlier U.S. Pat. No. 3,316,173 in which water is treated with bromine and wherein a strong base anion-exchange resin is used as a source of diatomic or elemental bromine, the bromine being eluted from the resin to form a relatively concentrated aqueous solution, which is subsequently mixed with a larger volume of water, such as the water in a swimming pool, to provide a bacteriocidal concentration of bromine. In accordance with the teachings of U.S. Pat. No. 3,316,173, the bromine is eluted from the resin in concentration of from 10 to 10,000 p.p.m., which is stated to be far above physiologically acceptable levels of bromine in water for human consumption.
Still another prior art disclosure dealing with the treatment of water to effect disinfection thereof or to control microorganisms therein in U.S. Pat. No. 3,462,363. This patent refers to U.S. Pat. No. 3,316,173 and points out that, because the residual halogen picked up by water treated by strong base quaternary ammonium anion-exchange resins in polybromide form, prepared pursuant to the aforementioned U.S. Pat. No. 3,316,173, or in strong base quaternary ammonium anion-exchange resins in other previously known polyhalide forms, is unduly high, as is directly indicated in U.S. Pat. No. 3,462,363, to effect substantial reduction in the content of residual halogen in the finally treated water, said U.S. Pat. No. 3,462,363 finds it necessary to resort to a two-step or tandem treatment with a strong base quaternary ammonium anion-exchange resin in a polyhalide form, namely, the scavenging resin.
As will be seen below, in light of the description of my present invention, and the purposes and objects of my invention, such are readily distinguished from the disclosures in the aformentioned patents. As will also be pointed out below, the teaching and disclosures of the aforementioned U.S. Pat. Nos. 3,817,860; 4,187,183; 4,190,529; 3,316,173 and 3,462,363, as well as the published articles referred to above which deal with experimental work related to U.S. Pat. No. 3,817,860, fail to provide any teachings of my present invention and the advantages that are achieved thereby over the disclosures of said prior art references taken singly or as a whole.
By way of further background information, relevant to my present invention, it has been known, generally speaking, that under certain limited conditions, while the U.S. Environmental Protection Agency (USEPA) approves of the use of iodine and also of bromine as drinking water disinfectants, up to the present time, policy statements in reference thereto which issued in 1973 by USEPA have remained fundamentally unchanged. Chlorination of water is regarded as a safe procedure and it is, and long has been, in common usage for public water supply as well as for general use. On the other hand, in the case of iodinated or brominated water for human usage for drinking purposes, the policy promulgated by USEPA in 1973 indicates that the presence of iodine or bromine in emergency situations in water supplies would be considered tolerable or not harmful where the consumption of iodinated or brominated water is brief, for instance, of the order of not more than about 3 weeks, and where the iodine or bromine content of the water is in the range of about 0.5 to 1.0 mg. of iodine or bromine per liter. In general, however, iodine disinfection of public water supplies is not recommended because of possible adverse effects on individuals with impaired thyroid function or on the unborn child. In any event, so fas as I am at present aware, no disinfecting systems heretofore have been developed, involving the use of iodine or bromine, which are acceptable and approved for long term or in-line usage for disinfecting water because the effluent from all known systems, of which I am aware, contains an unacceptably high level of residual iodine/iodide or bromine/bromide. Thus, while the disclosures of such prior patents as those referred to above, indicate or purport to meet USEPA conditions for long term usage, so far as I am aware they possess the deficiency that the effluents from the triiodide or polybromide strongly basic anion-exchange resins thereof still contain sufficient residual iodine/iodide or bromine which precludes their acceptability for use in public water supply systems, particularly where the treated water is intended for long term or in-line drinking purposes.
The ultimate design of an iodine or bromine bacteriocidal system would be a demand mechanism, i.e. bacteriocidal materials are released only as demanded by the presence of microorganisms in the water to be treated.
In the aforementioned U.S. Pat. Nos. 3,187,860; 4,187,183; 4,190,529, as discussed, in part, above, as well as in U.S. Pat. No. 3,923,665, methods are disclosed for making bacteriocidal resins and a formula is specified in said U.S. Pat. Nos. 4,187,183 and 4,190,529 which provides conditions to be satisfied for producing certain of such bacteriocidal resins. Generally speaking, over and above what has heretofore been stated in regard thereto, this formula centers around the use of potassium iodide (KI) and elemental iodine (I.sub.2) to form "triiodide" ions that can be attached to a synthetic ion exchange resin. This is accomplished by preparing a stoichiometrically balanced solution of I.sub.2 in KI. The resin is then stirred into the solution and allowed to react. The aforesaid U.S. Pat. Nos. 4,187,183 and 4,190,529 claim that the polyhalides, specifically triiodide, occupy certain resin sites as follows: EQU a is I.sup.-.sub.3- EQU b is I.sup.-.sub.5
wherein:
a=0.4 to 0.8 of the exchange sites PA1 b=0.1 to 0.3 of the exchange sites PA1 a+b=a predominant number of the anion sites available for exhange and a+2 (b) equals or exceeds 1.0.
As has also previously been discussed above, reference is made in certain of said patents for the need to use a bed of scavenger resin downstream of the triiodide resin in order to cope with the relatively high levels of iodine/iodide in the effluent from the system, the scavenger resin serving to react with the excess iodine/iodide in order to remove it from water streams.